With regard to AT&T’s non-denial denial about whether they played any role in Apple’s removal of Google Voice apps from the App Store, recall what AT&T stated regarding the iPhone SlingPlayer app in May:

AT&T told Wired.com that a 3G-capable SlingPlayer for iPhone would
violate AT&T’s terms of service. An AT&T spokesman explained that
a 3G-capable SlingPlayer could potentially strain AT&T’s 3g
network.

“Slingbox, which would use large amounts of wireless network
capacity, could create congestion and potentially prevent other
customers from using the network,” an AT&T spokesman said. “The
application does not run on our 3G wireless network. Applications
like this, which redirects a TV signal to a personal computer, are
specifically prohibited under our terms of service. We consider
smartphones like the iPhone to be personal computers in that they
have the same hardware and software attributes as PCs.”

So, sure, it’s true that “AT&T does not manage or approve applications for the App Store”. But AT&T does require that the apps Apple approves for use in the U.S. adhere to AT&T’s interpretation of their own terms of service.